Method and apparatus for hair removal

ABSTRACT

A laser treatment method for removing unwanted human hair includes irradiating a treatment site with post-coherent light of selected wavelength and peak power level and post duration, and repeating the post-coherent laser irradiation on one or more subsequent occasions with selected light parameters. A therapeutic treatment device has a laser and associated support elements and has a dermatology handpiece with a distance gage, a conduit for applying pressure and/or cooling to the treatment site and, optionally, cooling elements.

BACKGROUND

Human skin contains a number of appendages. Vascular and lymphaticchannels provide for nutrition, healing and transport. Sweat andsebaceous glands provide respectively for thermal control andlubrication. Pigmented structures provide for sun protection. Hairfollicles and individual hairs provide for insulation, protection andindividual differentiation.

Growth of each hair is originated by germinative fibroblast cells in thebasal layer of the epidermis. The hair grows both outwards and inwardsduring its growth cycle, and the follicle develops as an encapsulatingpouch extending beyond the epidermis and down several millimeters indepth to the subcutaneous fat. Hair remains attached to the base of thefollicle, where a capillary network develops to provide nourishment.During the anagenic growth phase, hair matrix cells divide rapidly andmigrate upwards to form the shaft. A subsequent catagenic phase ismarked by cessation of mitosis, and the reabsorption of the lower partof the follicle. Capillary nourishment is greatly reduced during thisphase. In this or the final telogenic (resting) phase, the hair fallsout and a new hair may replace it in a new growth cycle. At anyparticular time, approximately 10% of scalp hairs will be in telogenicmode.

The growth cycle varies with anatomical location from as little as 3months for facial hair to as much as 7 years on the scalp. Hair in highfriction pubic areas may be retained by the body as protection and maynot shed at all.

The hair follicle consists of a mixture of germinative cells andmelanocytes. Sebaceous cells empty into the follicle, providing alipid-rich environment. The follicle is typically 0.1 mm in diameter andmay extend to 4 mm in depth. The average hair diameter within thefollicle is 60 um. Hair itself is generated as an accumulation of dead(keratinized) cells. Structurally it consists of two or three discretelayers, as shown in FIG. 1. The outer cuticle layer consists of a singlelayer of overlapping flat cells like the scales of a fish. This acts asa protective barrier. An inner cortex layer contains any pigment whichmay be present (pigment may also reside in melanocytes lining thefollicle). Pigment may exist as two melanin forms. Eumelanin isresponsible for brown/black coloration and pheomelanin is responsiblefor red/blonde coloration. Larger, fully developed terminal hairs alsocontain a core known as the medulla.

In the lower follicular region, a bulge is formed where the arrectorpili muscle contacts the follicle. This muscle controls movement andorientation of the hair and may, under appropriate stimuli, render thehair vertical with respect to the skin surface. The bulge area has oneof the fastest rates of cell division found in mammals, stimulated bygrowth factors from the lower papilla area.

While the hair follicle and hair contained therein function at severaldifferent levels, excess body hair does present a cosmetic problem forhirsute females. As a consequence, many individuals undergo hair removaltreatments. Conventional techniques, including electrolysis, shaving,wax epilation and tweezing, are often painful and temporary.

Electrolysis is used by an estimated 1 million women in the UnitedStates. Two techniques dominate the electrolysis field. Galvanic (DC)current can be passed down a fine needle inserted into the follicle.This converts tissue saline locally to sodium hydroxide, which destroysthe follicle. Alternatively, the thermolysis technique utilizes an ACcurrent to directly heat and thereby destroy the papilla. Someclinicians utilize a combination approach of these two electrolysistechniques. All electrolysis methods treat a single follicle at anytime, in a painful procedure which can require analgesia. Disposableneedles are used in this non-permanent, time consuming, multipletreatment technique.

Several contemporary photonics techniques have been evaluated.

In 1993, Thermotrex Corporation was assigned two Hair Removal Device andMethod patents (U.S. Pat. Nos. 5,226,907 and 5,425,728) based on the useof an externally applied chromophore to enhance local absorption oflaser light. In these patents, a topically applied substance is said topenetrate to the full depth of the root of the follicle. The substancescited include permanent hair dyes, suspensions of carbon particles andphotosensitizing compounds. A subsequent application of laser light issaid to induce a photothermal reaction which destroys the follicle and asurrounding tissue area.

The compounds cited by Thermolase in their patents will probablydemonstrate follicular selectivity. Many other topical compounds, andsome systemic compounds, exist as candidates. Liposomal or lipophiliccompounds may favor the lipid rich environment. Alternatively, solventssuch as ethanol may be used to de-lipidize or re-organize the sebum, andthereby open the follicular passageways. Deposition of hydrophilic drugsmay be facilitated by the action of wetting agents such as sodium laurylsulfate, which may promote the creation of an emulsion. Particle sizeclearly plays a role in terms of ability to penetrate through narrowepidermal structures and along the follicular duct. The approach citedin this invention may work, although its practice involves the use ofexpensive laser equipment. Further, the use of topical compoundsprolongs treatment and raises potential risk.

A second technique has been studied and reported by Drs. MelanieGrossman and Rox Anderson whereby single high energy normal mode Rubylaser pulses are applied to the skin in the absence of an externallyapplied chromophore. No issued patent has been awarded covering thiswork. In this method, the optical target is the melanin within the innercortex layer and the pigment-bearing melanocytes lining the follicle.High fluences of up to 60 J/sq.cm. are utilized in large spotsizes, withshort pulsewidths of the order of 150 μsec and a wavelength of 694 nm.This technique employs a number of natural phenomena to enhance effecton the deep follicular component. A large applied spotsize and highfluence allow for maximum depth of penetration. Concurrent coolingspares bulk tissue structures from the edema and general damage whichcan result from the use of fluences of this magnitude. Intimateindex-matched contact of the custom handpiece with the tissue minimizesreflection loss. However, the short pulsewidths used in this approachare unlikely to efficiently transfer heat to the entire follicularstructure. The Ruby laser is not readily capable of the requisitemillisecond-domain pulses necessary to effect a true thermal mechanism.

A third approach, utilizing the Q-Switched Ruby laser, was disclosed byNardo Zaias in his 1990 U.S. Pat. No. 5,059,192. This patent cited theuse of a Q-Switched Ruby laser at 694 nm, with 3-8 mm spotsize andaround 8 J/sq.cm. Pulsewidth was in the range 30-40 nanoseconds. Lightenergy administered in such a short pulsewidth will be well retained inthe melanocytes lining the follicle. This approach will providepotential for melanocyte destruction and perhaps permanentdepigmentation or destruction of the hair, but likely will not kill thefollicle itself, since the pulsewidth is insufficiently long to conductheat away from the targeted melanin granules.

Other approaches have been described.

In 1967, U.S. Pat. No. 3,538,919 was filed by R. Meyer. Meyer cited theplacement of a fiber directly into the follicle into which a total of30-40 J/cm² of light was subsequently launched. This fluence wasadministered over a period of 1-2 milliseconds, preferably by a normalmode Ruby or Nd:YAG laser. Use of a 50 um fiber was cited. This fiberdiameter would theoretically fit into a 100 um follicle containing a 50um hair, but with some difficulty. Also, the technique would be timeconsuming to administer, on a single hair-by-hair process.

In 1970, Richard Harte filed U.S. Pat. No. 3,693,623, which also citedthe placement of a fiber directly into each follicle to be destroyed.The light source here was a xenon lamp, which applied up to 3 mJ to eachfollicle, in an interval of less than 3 msec. This technique againaddresses each hair individually in a tedious and difficult toadminister process.

In 1973, Carol Block filed U.S. Pat. No. 3,834,391, which similarlyaddressed the placement of a fiber at the follicular entrance. Lightsource was unspecified. This patent introduced the concept of the use ofmineral oil, said to facilitate light conduction, presumably by indexmatching. No additional chromophore was added. This technique in thispatent calls for the destruction of each hair on an individual basis ina tedious and difficult to administer process.

In 1981, H. Weissman filed a patent, later granted as U.S. Pat. No.4,388,924. This cited the devitalization of hair by the specificdestruction of the papillary blood supply. A narrow beam from an Argonlaser was directed onto the tissue. This light was said to be absorbedby the papillary plexus, causing heating and coagulation. Multiple 20-30millisecond exposures from a 0.5-2.5 Watt beam were cited. The hair wassubsequent tweezed from its follicle. This method suffers again from theindividual hair-by-hair approach, which is time consuming. Also, theselective destruction of the papillary plexus is unlikely to bepractical using a narrow beam Argon laser, with its limited penetrationdepth capabilities, since this supply resides at several millimeterdepth and is shielded by the overlying follicular structure. Indeed, novascular specific lasers are likely to exhibit adequate dermalpenetration.

In 1984, A. Sutton filed a patent, later granted as U.S. Pat. No.4,617,926. This provided for the use of a fiber without a core, intowhich an individual hair slides by 2-3 mm, completing the waveguidingaction. Different probes were cited, and about 1 Joule of energylaunched into the fiber, from an unspecified laser source. In analternative embodiment, the fiber is sharpened and inserted directlyinto the follicle. This technique is time consuming and tedious and islikely to result in rapid probe destruction.

SUMMARY OF THE INVENTION

The present invention comprises a laser treatment method and apparatusfor the removal of unwanted hair.

The treatment method, according to one embodiment of the invention,includes:

Irradiation of the skin uniformly with peak power level in the range1-500 Watts of coherent light, pulsewidth 1-99 milliseconds, spotsize1-3 mm, and wavelength in the range 650-1000 nm, controlling theparameters until desired endpoints are observed during treatment,consisting of `curling` or residual hair, perifollicular edema,erythema, blanching and purpura.

Allowing the skin to heal for a period of 1-3 months.

Irradiating on 0-8 subsequent occasions with additional exposures.

One apparatus for practicing the foregoing embodiment consists of:

A modified high power semiconductor diode laser system with pulsewidthvariable from 1-99 milliseconds together with an adjunctive coolingapparatus and method of applying suction or pressure to betterdifferentiate and flatten follicular structures.

The invention incorporates a modified laser apparatus with newapplication, together with a novel treatment method for the eradicationof unwanted hair. The specific target for the laser radiation is themelanin within the hair shaft and within the melanocytes lining thefollicular duct. Pulsewidth is controlled for a direct thermal effectfrom a single pulse. The new treatment method thus developed presentsthe potential for numerous significant advantages relating to theinduction of precise localized thermal damage with highly penetrativecoherent light. Damage thereby induced should be permanent andselective. Also, the apparatus cited in the invention has lower cost andgreater portability than alternative apparatus, thus presenting cost andconvenience advantages to potential patients.

This development of a clinically effective therapeutic treatment using acarefully controlled modified laser apparatus with associatedminimization of adverse effects is a major improvement and advance overcurrent options.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference may be made to the following detailed description and theaccompanying drawings, in which:

FIG. 1 is a sketch of the anatomy of a hair follicle.

FIG. 2 is a graph of the absorption characteristics of whole blood, alocal chromophore.

FIG. 3 is a graph of the absorption characteristics of water, a localchromophore.

FIG. 4 is a graph of the absorption characteristics of melanin, thetarget chromophore.

FIG. 5 is a sketch illustrating the anticipated thermal effectsassociated with the application of millisecond-domain near infra-redlight on the follicle.

FIG. 6 is a schematic representation of the preferred treatmentapparatus according to one embodiment of the invention.

DESCRIPTION OF ILLUSTRATED EMBODIMENTS

The follicle represents a well defined physical target, which may beassumed to extend to a depth of approximately 4 mm, with a mean diameterof 100 μm. The hair within the follicle may have a diameter up to 60 um.The follicle and contained hair are well differentiated optically bymelanocytes and melanin granules, which constitute the direct target inthis invention.

It is necessary to consider the optical properties of the constituentskin layers and follicular components in order to assess the impact ofthe proposed treatment in context.

The skin is a complex, highly dynamic, variable and multi-layeredoptical medium. Chromophores tend to be confined to discrete structureswhich may be considered as having a discrete location, but scatteringcenters tend to be distributed uniformly throughout this opticallyturbid media. The dominant chromophores are melanin and the hemoglobins.Melanin is found in the basal layer of the epidermis, usually in auniform distribution, although cellular activity of melanocytes can varydramatically by anatomical region or between individuals. Melanin isalso found in melanocytes lining the hair follicle and within individualhairs, giving them their characteristic color. The hemoglobins, beingblood borne, may be considered to be relatively uniformly distributedthroughout the dermis, although discrete upper and lower horizontalplexi are found in the papillary and reticular dermis respectively.Local blood (hemoglobin) concentration may be enhanced aroundproliferative structures, such as the hair follicle, any malignant orbenign growth, or around a wound healing zone.

Optical transport processes within the skin include reflection (specularand diffuse), absorption and scattering.

In the highly turbid media of skin, many scattering events occur andthis process plays a significant role in the definition of finalabsorption location. Scattering results from inhomogeneities in amedium's refractive index, corresponding to physical inhomogeneitiessuch as the collagen and elastin fibers and vascular channels. Thenature of the scattering process is highly dependent on the dimensionsof the scattering center. Where scattering centers are of dimensionsignificantly less than 1 um, the scattering is weak and isotropic, oromnidirectional. This Rayleigh scattering, as commonly found in skin,results in an apparent spreading of the incident beam. Where scatteringdimensions approximate beam wavelength, Mie scattering dominates,producing a much stronger, forward directed scattering, although stillat some angle, usually within about 30' of the incident beam. Miescattering is dominant in skin at visible wavelengths. When thedimension of the scattering center greatly exceeds the wavelength of thelight, Fresnel reflection occurs, and a proportion of the incidentphotons may undergo a reversal in direction or reflection event.Reflection is a form of scattering, characterized by transitions betweenregions of macroscopically different refractive index.

With multiple such scattering events, the individual photons may havetheir directions reversed or significantly altered, resulting in a muchless well defined beam as depth into tissue progresses. The process hasa wavelength dependence. In broad terms, shorter `blue` wavelengths areimpacted by scattering to a greater extent, since they approximate thedimension of the scattering centers and experience Mie scattering.Longer `red` wavelengths experience the weaker Rayleigh scattering andare less affected.

Absorption is dominated by the hemoglobins and melanin. (Tissue waterplays an insignificant role in the spectral region of interest from650-1000 nm). As shown in FIG. 4, melanin has a monotonically decreasingabsorption profile from the ultraviolet region to the near infra-redregion, where absorption becomes virtually negligible around 1000 nm.The hemoglobins also tend to have an absorption characteristic whichdecreases towards the infra-red, though with localized absorption peakscorresponding to molecular and atomic transitions. Oxy-hemoglobin hasabsorption peaks around 430, 540 and 577 nm, while de-oxygenatedhemoglobin has absorption peaks around 450 and 560 nm. FIG. 2 shows theabsorption characteristics of whole blood, which is considered to bepartially oxygenated, at the 80% level. Other blood borne chromophoresinclude bilirubin, which has a broad absorption band around 450 nm, andbeta-carotene, with a broad absorption band in the region 450-500 nm.

In terms of optimizing penetration and selective absorption within skin,the emphasis of this invention is on the minimization of scattering andunwanted absorption. Such considerations assume particular importance inhair removal, where deep-lying structures are targeted. An opticalwindow, with minimal absorption and scattering, exists between 600-1000nm, where depth of penetration extends to several mm. This region alsoexhibits selective absorption locally within the melanocytes lining thefollicle and in the melanin within the hair itself, since melanin hasresidual absorption in this region. The region around 800-850 nm isparticularly useful, as it possesses significant melanin absorption,with minimal competitive absorption from water and blood components.This region is cited in the preferred embodiment of this invention.

Thermal considerations are also significant. Given the average 100 μmdimension of the follicle, an exposure duration was derived by theinventor to induce mechanical or thermal effects. The most selectivethermolysis will occur when exposure time is less than thecharacteristic thermal conduction time constant of this target. Exposuretimes significantly shorter than this may result in a mechanicalprocess, while significantly longer exposures will result in heattransfer to the surroundings. For uniform absorption in a 100 μmdimension target such as the hair follicle, the thermal conduction time(calculated by T=d² /4×K, where K=thermal diffusivity) may be calculatedas 19 msec. During the course of this relaxation time interval, heatwill spread to affect a 100 μm region around the follicle. This numberprovides a useful estimate of the transition range from photo-mechanicalcontainment to proximal photo-thermal effect, although exposureintervals somewhat shorter than this time constant may still result in athermal mechanism. In broad terms, a sub-millisecond exposure willresult in conduction of less than 20 μm and a mechanical effect, while a1-30 millisecond exposure will likely result in a specific localizedthermal effect within the follicle and surrounding structure, to aradius of 20-120 μm. A longer exposure will extend the thermal damagefurther into the perifollicular dermis. This may occasionally bedesirable, as when larger hairs are being exposed.

Calculation of Thresholds for Selective Damage

It is illustrative to calculate the necessary fluence level at which theskin area around the follicle should be exposed in order to effect thecoagulative necrosis of the follicular structure. This calculation isundertaken by the inventor in the material that follows. Severalassumptions are necessary. These relate to exposure time, targetcharacteristics, and laser wavelength. In the process of thecalculations, an optical distribution by absorbed tissue segment isfirst derived. This may be converted to a thermal distribution by meansof the formula:

    temperature rise=E/C×M

where E=energy deposited in tissue segment=no. of photons×photon energyC=specific heat capacity of tissue M=mass of absorbing tissue segment.

It is assumed here that a temperature rise of at least 42° C. isrequired, representing an increase from 38° C. to 80° C. Tissuestructures will undergo coagulative necrosis at this temperature formillisecond-domain exposures.

It is further assumed that melanin is uniformly distributed across thefollicular dimension and that any light impinging on the follicle at theirradiating wavelength (in the region 650-1000 nm) will be completelyabsorbed in a uniform fashion across the dimension.

It is assumed that 20% of the incident energy from each exposure pulsewithin a (nominal) grid of contiguous 3 mm spots is absorbed in thefollicle.

Three specific instances are presented below:

Firstly, a single 1 millisecond exposure will be considered. During thistime interval, heat will spread a distance of 20 μm away from theabsorbing location, assuming no phase change of the media. Hence, if theinitial absorbing location is assumed to have a cross sectional diameterof 100 μm, a total width of tissue of 140 μm will be affected. If lengthis 2 mm, volume of heated site is 0.000043 cm³. Its mass is 0.000043 g.

In order to undergo a temperature rise of at least 42° C., this tissuevolume must absorb at least 0.0077 Joules of energy. Hence, the 3 mmbeam spot must impart 0.038 Joules of energy within the 1 millisecondexposure, since only 20% of the incident light is usefully absorbed.This implies that the beam should have a peak power of over 38 Watts.

Secondly, a single 5 millisecond exposure will be considered. Here,radius of conduction would increase to 100 μm, and affected mass ofabsorbing site to 0.000062 cm³. This larger volume would need anirradiation of at least 0.055 Joule in this 5 millisecond period. Peakpower would then need to be over 10 Watts.

Thirdly, if a 20 millisecond exposure were employed, radius ofconduction would increase to 100 um, and affected mass of absorbing siteto 0.00009 g. This larger volume would need an irradiation of at least0.079 J in this 20 millisecond period. This implies that the beam shouldhave a peak power of at least 4 Watts.

In practice, the peak powers cited above may be low for a number ofreasons. Firstly, hair follicles may absorb less than 20% of theincident light, especially where the structure is lightly pigmented.Secondly, it may be necessary to involve more than 2 mm of thefollicular length. Thirdly, a temperature rise of more than 42° C. maybe required. Taken together, these factors may demand more than twicethe peak power values calculated previously. The table below shows thelikely power range as a function of irradiation pulsewidth. Preciseoptimum pulsewidth is not known under all circumstances, but is likelyto be in the range 1-20 milliseconds, based on the preceding argument.For illustrative purposes, the effect on a hair follicle of a 50 Watt, 5millisecond pulse is shown in FIG. 5. This plot illustrates that theabsorbing follicle achieves a peak temperature of 100° C., where it isanchored. (Significantly higher incident energy would be required toimpart the necessary latent heat to ensure a phase change). The dottedline in this figure shows the thermal damage envelope extending out by50 μm radially.

The table below shows suggested useful power ranges, based on theinventor's calculations, to produce the desired specific thermal effect.

    ______________________________________                                                       peak power range for follicular necrosis                       exposure pulsewidth (msec)                                                                   (Watts)                                                        ______________________________________                                                1      38-100                                                                 5      11-28                                                                  20     4-10                                                           ______________________________________                                         Note: A wavelength in the region of 650-1000 nm is assumed. This light        will uniformly irradiate the tissue, by means of carefully placed             contiguous spots, applied manually or with an automatic scanner. Uniform      absorption is assumed across the follicular dimension. The values shown       are illustrative only, and do not capture all embodiments of the              invention.                                                               

From the above theoretical analysis, it has been found a coherent lasersource emitting in the wavelength region 650-1000 nm, with variablepulsewidth and spotsize capabilities, meets the conditions required forremoval of unwanted hair by means of the coagulative necrosis of thefollicular structures.

In the calculations above, it is understood that a typical follicularstructure may be selectively damaged by use of a power level of up to100 Watts, and an exposure pulsewidth preferably in the range 1-20milliseconds. To allow for modeling limitations, that a source with upto 500 Watt peak power capability and pulsewidth variability in therange 1-99 milliseconds is deemed preferable to provide clinicalflexibility.

The invention is further refined by addition of means to betterdifferentiate the follicular structure. The first such means stimulatesthe arrector pili muscle group, which controls the angle at which thehair rests. In response to external stimuli such as cold, this musclegroup will orient the hair in a perpendicular fashion. This is desirableas it allows for more uniform exposure of the entire follicularstructure to the incident light. Accordingly, the invention incorporatesa method for the reduction of skin temperature prior to exposure toeffect this re-alignment of the hair. This further allows for desirablecooling of the superficial skin layers.

It is also desirable to reduce the apparent depth of the follicle, sincethis depth presents a limitation in terms of the ability of the light toimpact the entire follicular pathway. This may be achieved by means ofthe application of suction or pressure, which draws the hair towards theskin surface or flattens local skin structures. This has the furtheradvantage of temporarily restricting local blood flow and itscompetitive characteristics in terms of light absorption.

Apparatus

It was determined, in accord with the invention, that some manifestationof diode laser technology is of providing the requisite parameter set.

Semiconductor diode laser technology, first developed in 1962, todayfinds application in devices ranging from consumer electronics andcommunications to medicine.

A basic system, in the high power configuration envisaged here, has ascore components an electronic power supply coupled to a semiconductorcrystal encapsulated in an optical chamber capable of capturing andharnessing optical emissions from the crystal. When a large directcurrent is passed through the crystal, optical emission is generated andamplified. A beam of light results, with a high degree of brightness anddirectionality.

The basic system is further refined by means of the addition ofthermo-electric cooling circuitry for temperature stabilization and ofelectronic circuitry for exposure control and pulsewidth generation.Maintenance needs are minimal, with a 5000+ hour life on the sourcesequating to several years of use.

Individual diode elements have limited output power capability and beamshapes which are not amenable to ease of delivery to distant sites.Recent efforts have concentrated on beam shaping and combination ofbeams from a plurality of single elements. Each single element candeliver up to 1 Watt of CW power. Under certain circumstances, higherpeak power may be obtained from each diode if higher current is driventhrough the diode for a short period of time at a low duty cycle. Forexample, a diode element rated for 1 Watt CW may be driven at 2 Wattsfor a millisecond domain exposure period.

As a consequence, by means of the combination of beams from many suchelements on diode bars, it is now possible to deliver tens or hundredsof watts of diode laser light through flexible fiber optical cable to adistant site. These high power levels as recently demonstrated by otherinventors have made possible the new treatment concept outlinedpreviously, in which such a source, appropriately modified, may be usedfor the current application.

A number of medical device companies have packaged diode laser systemsfor medical use, based on the above core subcomponents. Use of theirfinished systems is advocated for urology, gynecology, general andplastic surgery, gastroenterology and ENT. None of these applicationsinvolves the direct targeting of the follicular structure.

Diode laser systems as described above have been utilized for generalsurgical applications on soft tissue, whereby a non-specific cuttingaction results from the delivery of long pulses of light (>100milliseconds pulsewidths are available from the devices), with powerlevels in the range 1-60 Watts. In this mode, such a device acts as anoptical scalpel, with some associated coagulative potential. Shorterpulsewidth selective surgery has not been explored by medicalmanufacturers of this technology.

One embodiment of the invention involves the modification of such asystem by means of electronic control circuitry to obtain shorterpulsewidth (1-99 millisecond) operation.

The practice of the invention harnesses the specific targeting potentialof the device by means of a careful control and administration of theparameters as modeled previously. By this means, light is to passthrough overlying tissue, affecting mainly the desired target follicularstructures. Direct targeting of hair follicles with a high peak power(˜1-500 Watts) and short pulsewidth diode source has never previouslybeen reported.

The apparatus is further refined in the invention by addition of meansto better differentiate the follicular structure. For example, the hairtypically resides at an angle controlled by the arrector pili musclegroup. In response to external stimuli such as cold, this muscle groupwill orient the hair in a perpendicular fashion. Such orientation allowsfor more uniform exposure of the entire follicular structure to theincident light. Accordingly, the invention incorporates a method for thereduction of skin temperature prior to exposure. This further allows fordesirable cooling of the superficial skin layers. The method employed inthe apparatus incorporates a cooled handpiece or cooled flowing gas.

It is also desirable to reduce the apparent depth of the follicle, sincethis depth presents a limitation in terms of the ability of the light toimpact the entire follicular pathway. This is achieved in the inventionby means of the application of suction or pressure, which flattenstissue structures or draws the hair towards the skin surface. This hasthe further advantage of temporarily restricting local blood flow andits competitive characteristics in terms of light absorption. A positiveor negative pressure is applied in the apparatus by means of a gaseousduct within the handpiece, and gas flow originating from the mainconsole. An inert gas may be employed, which may be cooled, furtherimproving the treatment by reducing the risk of combustion associatedwith laser light.

The invention consists of a clinical treatment methodology for theeradication of unwanted body hair, described in the next section. Thetreatment method employs modified specific optical apparatus which isdescribed in this section in terms of preferred and alternativeembodiments. The combination of parameters described below is deemedunique and advantageous for Hair Removal.

One preferred specification for the device is listed below:

    ______________________________________                                        Host material                                                                            GaAs semiconductor laser source                                    wavelength range                                                                         800-850 nm                                                         pulsewidth 1-99 milliseconds                                                  power level                                                                              1-500 Watt, 1 Watt increments                                      repetition rate                                                                          1-20 Hz.                                                           spot size on skin                                                                        1-3 mm, variable                                                   delivery system                                                                          fiber, with dermatology handpiece termination                      handpiece  thermoelectrically cooled, with flowing gas                                   ports                                                              laser cooling                                                                            thermoelectric                                                     method                                                                        skin cooling                                                                             cooled gas (may be inert) and/or cooled                            method     handpiece                                                          pulsing method                                                                           electrical                                                         aiming beam                                                                              red diode or helium neon laser (0.5-10 mW)                         skin treatment                                                                           may employ a scanner to enhance uniformity                         method                                                                        ______________________________________                                    

This preferred embodiment can specifically be utilized for the removalof unwanted hair.

A second alternative embodiment utilizes a different semiconductormaterial variant producing a wavelength in the range 650-1000 nm, with apeak power level in the range 1-500 Watts.

A third alternative embodiment utilizes a second host material `pumped`by the diode laser. This host material, which itself would then lase ata different wavelength, might consist of a polymer encapsulated dyematerial, or some other glass or crystal structure doped with lasingions.

All of the envisaged embodiments produce red or near infra-red lightwith pulsewidths and power levels amenable to the treatment of thetargeted follicular structures as calculated previously.

This first preferred embodiment is shown in FIG. 6.

The system consists of a set of arrays of individual laser diodescontained within a compact cabinet (2). The cabinet also containselectronic and temperature control components. Triggering of pulses isprovided via a separate footswitch (1) adjoined to the main console at aconnector (3). Light from the intemal diodes is collected internally ina set of individual small diameter fibers constituting a bundle. Thisbundle is grouped together physically within the cabinetry enclosure.Light transmitted through the bundle or fiber may be coupled via a highefficiency connector (4) into a single larger diameter fiber or lightguide (5). A separate cooling tube (6) adjoins the fiber or light guideto provide chilled gas or water to the handpiece (7), which mayseparately be thermo-electrically cooled. This tube and the light guidejoin the handpiece at two ports (9). The cooling tube (6) allows for theapplication of positive or negative pressure by means of cooled gas orliquid. The cooling tube adjoins the cabinet at a junction port (12).The optical delivery media is coupled into a handpiece (7) containingfocusing lenses. These lenses, together with a distance gauge (8),provide precise positioning and focusing onto the patient's skin (9).The handpiece (7) may itself be chilled by means of flowing chilledwater or by use of a miniature thermoelectric element. One of thehandpiece ports (9) allows for the application of a positive or negativepressure to the skin via a contact tube (13) which may be sealed. Powerlevel, repetition rate, and pulsewidth of the source are controlled bymeans of several electronic controls (10) which together provide accessto the specification set derived previously. Displays (11) permitverification of the selected parameter set.

An incorporated visible `aiming beam`, within the cabinetry enclosure,also delivered through the light guide, provides verification of theultimate placement of the invisible treatment laser spot.

Clinical Treatment Methodology

The goal of the treatment is to irreversibly damage the follicularstructures while leaving the surrounding normal skin intact andunaffected. Below is presented an optimal and novel therapeutictreatment methodology suitable for use in a variety of differentclinical applications.

A number of major advantages and conveniences are provided by thepresent treatment method, including:

1. The present methodology envisages the use of a specific parameter setchosen to provide optimum selectivity of damage to the target tissueonly. The damage is thermal in nature, calculated as necessary to effecta degree of controlled conduction to surrounding structures. Theepidermis and peri-vascular dermis are spared while damage isadministered, in a controlled fashion, uniformly throughout the targetedfollicular structures. This is turn minimizes any complicationsassociated with wound formation or unwanted cosmetic outcome.

2. All hairs within the irradiated area are treated simultaneously,eliminating the need for a tedious individualistic approach.

3. The invention provides for the use of narrow-band coherent infra-redlight. Such light is able to penetrate deep into the dermis with minimalscattering or competitive absorption and affect most of the follicularstructure.

4. The equipment used to provide the therapy can be manufactured atrelatively low cost and has great ease of portability. This willultimately result in greater patient access to the therapy.

5. The procedure is relatively gentle and painless, and obviates the useof multiple painful and non-permanent electrolysis treatments.

6. Several treatments are required. Each treatment will provide anoccasion for the physician to tailor the parameters to the individualneeds of the patient. Hence, the personal health, safety and cosmeticappearance of the skin are affected only to the extent required, and anyside effects minimized.

General Treatment Procedures and Preferred Details

A power level in the range 1-500 Watts is used, with 50 Watts of peakpower being a `typical` value. An associated spotsize of 1-3 mm isapplied uniformly over the entire affected tissue region. Uniformity maybe enhance by means of a laser scanner, providing for a controlledpattern of exposure on the skin. A Pulsewidth in the range of 1-99milliseconds will typically be used, with a value of 5 millisecondsbeing commonly selected. A wavelength in the range 800-850 nm ispreferred.

Hair within the site to be treated is counted, photographed and shavedbefore treatment. Desirable endpoints during treatment include somecurling of the remaining exposed hair shaft.

After treatment, the site may be somewhat blanched (whitened) due tosome coagulation of follicular appendages. Some fine purpura may also bepresent, as a result of some absorption by localized blood vessels,which will be coagulated.

An assessment will be made at the second visit relating to any color ortexture change of the skin. The vessel itself will also be graded forany lightening. Absence of any lightening or adverse effects will betaken as indicative of the need to increase energy or exposure time.Occurrence of significant adverse sequellae will be taken as indicativeof the need to decrease power and exposure parameters.

Detailed Protocol

The site to be treated is photographed under controlled conditions and ahair count attempted. It is further examined to detect the presence ofscarring or otherwise abnormal color or texture. Exposed hair is shaved.

On the first treatment visit, individual portions of the site to betreated are designated as test sites to which different carefully chosenparameters of laser light are applied. An initial set of parameterswould typically be: 30 Watts of light, 2 mm spotsize, 1 millisecondexposure time. Different sites within the designated area may be exposedwith different power levels or pulse durations. Some additional usefulparameter combinations include use of 30 Watts with 3 or 5 millisecondsexposure time. Lower power levels may be used with longer exposuretimes, such as the combination of 10 Watts with 5 or 20 milliseconds.Feedback is obtained from each application in terms of immediate tissueresponse and used to determine subsequent test site parameters. Desiredresponse includes a `curling` of any remaining hair above the skin. Iftissue damage is evident, power level and/or pulsewidth may bedecreased. If the desired endpoints of hair curling and local mild edemaare not observed, power level and/or exposure time may be increased.

Following treatment, a topical antibiotic ointment may be applied to thetreated site and the skin area covered with a dressing.

The patient will return after a specified healing period (usually 1-3months) for evaluation and further treatment. These additionaltreatments (typically up to 7) are administered with the parametersfound to result in minimal regrowth with minimal adverse sequellae.Parameters are adjusted if the response is inadequate (insufficient hairgrowth retardation) or too severe (induration, ulceration or pigmentarychange to the overlying epidermis). In the former case, applied powerand/or pulsewidth is increased, while in the latter case it isdecreased.

If a site has not responded (in terms of a reduction of hair count orgrowth delay) after a total of 6 treatments, treatment is to bediscontinued. In any event, the patient should be followed for up to oneyear to note any incidence of recurrence.

I claim:
 1. A laser treatment method for the removal of unwanted hairfrom the skin of a human, said method comprising the steps ofirradiatingon a first occasion a chosen section of human skin containing at leastone hair growing within a hair follicular structure with pulsed coherentlight with wavelength in the range 650-1000 nm, said light having a peakpower level in the range 1-500 Watts and a pulse duration of 1-99milliseconds, and said diameter of treatment beam being in the, range1-5 mm, allowing the skin to heal for a period of 1-3 months, andirradiating on each of a set of subsequent occasions with pulsedcoherent light with a wavelength in the range 650-1000 nm, said lighthaving a peak power level of 1-500 Watts and a pulse duration of 1-99milliseconds, and said diameter of treatment beam being in the range 1-5mm.
 2. The laser treatment method in claim 1 involving the permanentremoval, from a section of human skin, of hairs growing withinfollicular structures with minimal controlled damage to skin tissuesurrounding the follicular structures, comprising, the further stepsof:pre-cooling the treatment site and vertical alignment of the targetedhairs by means of application of chilled water or gas and/or by means ofthe direct thermo-electric cooling of the handpiece, application ofpositive or negative pressure to flatten local tissue structures andthereby restrict local blood flow, which competes for the laser light.3. The laser treatment method of claim 1 further characterized in thathair follicles are directly and indirectly destroyed by thermalconduction from absorbing melanin bearing structures, with a controlleddegree of coagulation of surrounding tissue structures.
 4. The lasertreatment method of claim 1 including the step of exposing the skinsubstantially uniformly exposed to the laser light by means of theadjunctive use of an optical scanner.
 5. The laser treatment method ofclaim 1 further characterized in that the laser is a red or infra-redcoherent laser source operating in the wavelength region 650-1000 nm,with peak power in the range 1-500 Watts and pulsewidth modified tooperate in the range 1-99 milliseconds.
 6. The laser treatment method ofclaim 1 further characterized in that said step of irradiating on asubsequent occasion is performed on each of a set of one to sevensubsequent occasions.